Fresh evidence to be screened by England's Channel 4 today of attacks on civilians and point blank executions of Tamil Tigers during Sri Lanka's civil war should spur the Gillard government to call for an independent investigation into war crimes during the civil war, says Greens Senator Lee Rhiannon.

"This new Channel 4 documentary, shot in the final stages of the war, shows the point blank execution of Tamil Tigers and the leader Velupillai Prabhakaran's 12 year old son as he was on his way to surrender," Senator Rhiannon said.

"Part two of 'The Killing Fields' documentary reportedly shows evidence of war crimes, including attacks on a UN food distribution station and shelling in a 'no fire' zone. It reveals some individuals suspected of war crimes now hold senior government positions.

"It is not enough for Sri Lanka's High Commissioner to Australia Admiral TSG Samarasinghe to claim Sri Lanka is conducting its own investigation into the later stage of the civil war.

"It is becoming more widely recognised that claims claim that Sri Lanka makes about investigating its own war crimes are a farce.

"It is time that the Gillard government backed calls from the UN Secretary-General's Panel of Experts, Amnesty International, the International Crisis Group and Human Rights Watch for war crimes to be properly addressed.

"Australia should also support a resolution being put by the US to the UN Human Rights council this week calling for greater accountability. While the draft resolution falls short of calling for an independent war crimes investigation it represents a constructive step forward.

"The Australian Greens reiterate calls for Prime Minister Gillard to ask the Sri Lankan government to recall the Sri Lankan High Commissioner pending an independent international war crimes investigation for incidents detailed in a submission made by the International Commission of Jurists Australia to the government.

"If the Sri Lankan government is unwilling to do this, Admiral TSG Samarasinghe should be expelled," Senator Rhiannon said.